Perception of radiant energy



E. BENSON ET AL PERCEPTION 0F RADIANT ENERGY s Sheets-Shet 1 Filed April 13, 1918 llillllllllllllll a) t/za'r o orroeya.

E. BENSON ET AL PERCEPTION 0F RADIANT ENERGY Jan, 20,

3 Sheets-Sheet 2 Filed April 13, 1918 lllllllllllllllll Bawson;

If ma E. BENSON ET AL PBRcEP'rIbN 0F RADIANT ENERGY Filed April 13, 1918 3 Sheets-Sheet 3 Z7268? Mrwegy-s.

Patented .lan. 20,1925

ELOF BENSO N, NEWTON HIGHLANDS, AND FRANCIS H, WILLIAMS, OF BOSTON,

MASSACHUSETTS.

PERCEPTION or RADIANT ENERGY.

Application filed. April 13, 1918. Serial No. 228,324.

To all whom it may concern:

Be it known that we, ELOF BnNsoN and FRANCIS H. WILIJAMS, citizens of the United States of America, and residents, respectively, of Newton Highlands, in the county of Middlesex, and Boston, in the county of Suffolk, both in the State of Massachusetts, have invented new and useful Improvements in the Perception of Radiant Energy, of which the following is a specification.

principles apply-ing the discovery of certain phenomena indicating the direct conversion into electrical currents, impulses or osclllations in a class of conductors [the electric manifestation in the conductor then being readily perceptible with the aid of known instruments] of such wave-motions or rad-iations. Radiations or wave-motions of the kind referred to, except electric waves, have not hitherto been observed to have the power to be converted into perceptible electrical currents or impulses, or directly to excite such currents or impulses in a conductor. Perception of or useful effect from radiations or wave-motions either of ponderable matter or the ether heretofore has been de'-. pendent upon receiving apparatus of marked limitations, such as the well-known receiving devices for electric radiations comprising oscillatory resonating circuits, including therein electric wave or oscillation rectifiers, thermo-electric couples, co-

herers or other detectors operating by changes of ohmic resistance, electrolytic changes, changes of ionic condition of a gaseous or other dielectric, by conversion to heat, by changes of electrostatic capacity, by demagnetization of amagnet, or by polar selectivity to current flow; and all as heretofore known, being sensitive only to electric radiant energy. Or such perception, for sound only, hitherto has been dependent upon hearing, assisted by direct amplification of the sound wave, or the operation of sound transmitters or microphones characterized by movable diaphragms or other parts bodily or dynamically vibrated by an incoming sound-wave desired to be perceived, the last mentioned apparatus for sound perception not being usefully sensitive directly to perceive electric radiations.

This invention comprises a new art or i method of perceiving, detecting or rendering useful for the purposes indicated and other purposes, wave-energy of the types mentioned, as well as a genus of apparatus for practising the said method.

The new art comprises simultaneous detection of electric radiations or Hertz waves,

inductive or radiant magnetic disturbances,

and sounds, apparatus employed for the practice of the invention being capable if desired of simultaneously receiving and converting into electric currents, impulses, or oscillations radiant electric energy such as ordinary wireless waves, inductive changes in the .field surrounding the detector, arid the acoustic vibrations of ponderable matter.

In certain forms of the invention, capacity to perceive an acoustic, magnetic or electric wave, or either, impinging on the apparatus employed is accompanied by capacity to detect or perceive thereby with substantial accuracy the direction of propagation of .the sound or electric radiation, and the invention also includes an art of and apparatus for determining the direction of propagation of such waves at the place at which they are perceived orobserved.

The apparatus selected to be herein shown and described as instances of one subordinate genus of the broader genus of apparatus adapted to be used in the practice of the art or method forming a part of the invention, is characteristically capable of developing a perceptible electric energy therein in response to exterior excitation by acoustic, radiant magnetic. electric and other radiations independently of the-dynamic motion,

'so far as known, of any of its parts, and independently of any source of energy within the apparatus other than the energy received from such radiation or wave-motion.

Radiations or wave-motions capable of so exciting the illustrative apparatus comprise sound waves in air or denser media, lying within a selective range of pitch or wavelength variable with changes in the apparatus; vibrations of acoustic type inaudible as sound; radiant electric and magnetic waves,

that apparatus of the genus in .also capable of excitation by t er radiaand changes in the magnetic or inductive field at the apparatus, and it may well be uestion is I the best instances of which we are now aware of devices for practicing the method or art.

We are aware of mere uses to which the invention may be applied without substantial change and within the expected skill of artisans almost as numerous as the arts aided by the application of electricity and ,for that reason we shall undertake to describe in this specification not all but only one specific application to use, with such illustrative instances of'the mode of and apparatus for effecting this result as are necessary to understand it. The devices are particularly useful for the selective determination of marine and submarine sounds, of marine and under-water emissions of an inductive or magnetic nature, and ofthe direction of their propagation, and the specific use elected to be described relates to thedistant detection of a submarine or surface vessel by such sounds or other radiations proceeding from the vessel, and the determination of us bearing and motions in respect to the observer.

In the accompanying drawings- Figure 1 is a diagram of apparatus representative in general of types ofv the apparatus employed;

Figure 2 it a diagram, Fig. 2 a section on an axial plane, and Fig. 2 an elevation of one form of wave-detector;

Figure 3 is, an axial section of another form of wave-detector;

Figure 4 is a similar section, and Fig. 4 an end elevation of another form of detector;

Figure 5 is an axial section, and Fig. 5 an elevation of another form of detector;

Figure 6 is a diagram section in the axial plane of an annular core for another form of wave-detector; and Fig. 6 is an axial" scction of another form of detector;

Figure 7 is an elevation of another form of detector;

Figure 8 is a perspective illustrating another form of wave-sensitive. instrument useful in the practice of the method;

Figure 9 is a side elevation of another form of detector;

-Fig ures 10 to 17, 17 and17" are diagrams explanatory of experimental evidence I of the nature of the phenomena utilized;

Figures '18 and 19 are diagrams illustrating operation of the, form of the device shown in Figs. 2 to 2".v p

Figure 20 is a similar diagram illustrating capacities of the form of the device shown in Fig. 3;

Figure 21;,is a diagram illustrating an employment 1' one form; of the apparatus for the reception of submarine signals;

Figures 22, 23, 24 and 25 are diagrams illustrating a method of shielding a detector from radiations propagated in certain directions;

Figure 26 is a diagram showing zones of silence and maximum response at a detector.

'Figure 26 is a similar diagram for another form of detector;

Figure 27 is a. vertical section through one 'form of mounting for the detector instrument;

Figure 28 is a vertical section showing another form of mounting for detector instruments I Figure 29 is a detail side elevation of the device of Fig. 28;

Figure 30 is a diagram in plan illustrating employment of devices corresponding to the invention for the detection of radiations from and the position of an emitter of submarine radiations, such as a submarine or other power boat; and

Figure 31 is a diagram of circuit connections.

During the course of a series of experi-' ments on forms of devices adapted to receive and transmit faint sounds received under water, we were led to conclude thatthe vigor and nature of extraneous sounds occurring in the neighborhood of an observing vessel or occasioned by the motion through the water of the audition instrument itself, or the necessary result of sounds emitted by trafiic on orin the waterintended to be observed, were such as to prevent useful observation under the very conditions in which such observation would prove of the most utility; for instance,

under conditions in which it is important to detect the approach and movement of an enemy submarine vessel or of an automobile torpedo, or to pick up signals or telephonic signals from another ship or shore station from a vessel underway. The

difficulty common to all of theprior art apparatus of which we are aware has been too great sensitiveness of the detector and transmitter device to all sounds, especially -to noises made on the ship carryin the ob-, serving instrument or resulting mm the progress of the ship or detector through the Water. I a

Not then being able to dispense with some form of vibrated diaphragm, we conceived the useful possibility of rendering much less sensitive than heretofore a transmitter,

such as the commonly employed microphone transmitter, and then observing the indications transmitted by such an instrument with the aid of an amplifying device, either the transmitter or the amplifier being adapted selectively to magnify or amplify the impulses transmitted with respect to the class of sounds sought to be preceived, and

to suppress or not so much to magnify the.

indications of extraneous noises acting to disturb the observation.

For this purpose we conceived using together a sensitive oscillation amplifier of any well-known type, and a circuit containing a source of energy, the amplifier, and a detector of selective and little sensitiveness. These experiments led to the discovery of a class of phenomena which we are at present able to assign to no wholly satisfactory theory, although by hypothesis. presently to be referred to we have been able to design instruments for predicted results and to obtain complete and satisfactory confirmation' in operation of the predicted behavior ofthe instruments. Wewill therefore explain the phenomena in question by reference to experimental reactions of apparatus in order to enable the operation of the devices and "practice of the art involved to be clearly understood, whatever the underlying physical explanation may be.

The apparatus comprises two parts, a sensitive amplifier A, Fig. 1, of alternating,

pulsating or oscillating currents, and re-' ceiving apparatus (Z whose indications are observed by the device A, which receiving apparatus in general we will hereinafter mention as the detector or detector circuit. Any suitably sensitive amplification device of the many known may be selected; but we prefer the well-known single or plural stage audion amplifier or thermonic repeater, ofwhich a species is shown having two audions A and A connected to act in succession on the incoming current at terminals a, a, to magnify the oscillation in two stages according to lmown constants inherent in the apparatus, without any considerable distortion in form of the indi cation received, thus enabling a very feeble oscillating current at a, a, to be powerfully heard at telephone T.

The instrument A desirably has constants such that at frequencies of about 100 per second the amplification of the impulse at T is not less than about 100 times the intensity of the received oscillation; at frequencies of 100 the amplification its not less than 250 times; at frequencies of 1100 amplification is above 300 times; and at frequencies upward of 1500 within the audible limit the amplification is in excess of 400 times the intensity of the incoming impulse. The preferred device comprises at the input end a step-up transformer 2 whose taining a battery I) or other sourse of energy, cathode filaments 7 and 27 and variable resistances 12, 14. The plates 8 of the audion A are connected by lead 15 to one plate of a condenser 16, and through a lead 18 and impedance coil 17 to oneterurinal of the primary of an output transformer20 whose secondary is in series with listening telephone T: and to the positive side of a battery or other source of constant potential 6 whose negative side is connected to the filament 7, as. at 29.

The other side of the condenser 16 is connected through lead- 22 to the grids 25 of the second audion A and also through lead 11, impedance coil 30 and lead 29 to the secondary of the input transformer 2, to the filament 7 of audion A, and to negative side of battery 6 The; plates 28, 28, of the audionA are connected to the primary of the transformer 20 of listening telephone T at 34:.

The ionizable gas between the respective filaments 7 and 2( and the respective anode plates 8 and 28 is thus placed under stress by the separate source of energy 6 which may be of about 130.volts potential.

It will be understood without detailed hot filaments-7 and the plates 8, said fiosv being a function of the "arying charge on the grids 5; and that in turn the flow of .current from b in the space betvieen-the V current'from 71 in the primary 20 is similarly augmented at A by the augmented charges originating at A. I

hen an ordinary microphone transmitter and separate mild source of energy, such as one cell of battery, is connected across the terminals a, a, the disturbance at the telephone T is too violent for any use p of the device whatever for the purposes contemplated. The negative side of the battery 72 may be connected to earth at E, if desired.

of soft iron about 2 feet wide, 2 feet long and about of an inch thick, is connected Referring now to Fig. 10, if a plate W i an,

- wound 011 'a tube f,

coilremains the same,

terminals a, a, by the wires w, w, there will be found an effect at the amplifier indicative of oscillating differences of potential between w and w related to the impact upon the. plate V of soundwaves, (or it may be of electric or magnetic waves associated with'the impact of the sound wave) at the plate W. The response of such a plate V to excitation by sound while distinct, is exceedingly faint. There is no source of energy whatever in this form of the apparatus in the circuit V, 'w, a, 2, a, w, except that created by the phenomenon in question.

If now the plate \[V is surrounded by a few turns w of wire not electrically connected thereto, and this wire is connected across the terminals a, a, a pla'iner response to the acoustic excitation of the plate W is atonce apparent. This may be due in part to the dynamic motion or bodily vibration in respect to such a coil 20 of portions of" the plate V, and if we can assume either a static charge in the coil or some magnetization of the plate, the behavior of the I device may be explained in part as that of a magnetophone or variable capacity transmitter of a type not wholly new; but the assumptions made are'not well founded, and

for on these suppositions.

Ifinstead of the plate (referring to Figs. 11 to 16;) 21 helix w' of copper wire a, the 'teleph'one T' will be found to receive very faintly loud, regular sounds in certain ranges ofpitch propagated at an angle to the axis of the helix. Sounds propagated along its axis are not received If a laminated (soft iron wlre) core c, Fig. 13, is entered in the helix, the effect sharply increases in magnitude. "If such a helix is Fig. 12, of glass or other non-conductor, the behavior of the creased by an inductive core 0', and more increased by a tubular soft-iron core 0. But if the tube f is made of a conductor, e. g. aluminum, insertion of a magnetically inductive core such as 0 is now without effect.

-If'the .core is a magnet, the effect is "-markedly dampened or reduced. If a constant source. of energy such as one cell or more of a battery is'put in circuit with a, a, the effect ceases.

If during the experiment such a helix and inductive soft-iron core is turned perpendicular to the horizon, in a city, the observer will at once note the increase above his unaided hearing of sounds of trafiic, and predominantly of sounds which we have identified as beginning and ending with and changing inpitch with the speeds of and in some way due to the operation of electric motors. Time of propagation of this type nearly at the maximum all ofthe phenomena can 'not be accounted" the efi'ect being inof excitation from a known source at a distance is not at the expected velocity of sound in air but is instantaneous within such mensuration as we have attempted, and is suspected to be at the velocity of light. Eachcoil selects from its exciting radiations, whether acoustic, electric or magnetic, and repro uces at T, undulations corresponding to sounds ofpitches and their overtonespeculiar to the particular coil, and probably dependent onthe electrical resonance of the closed circuit'including it, the character of its core, if any, and the disposition of-its spires, as well as upon the periodicity of-the waves, or trains of" waves, producing the disturbance. I

The observer when able to identify a source of the sound most loudly heard, such as a running motor or dynamo of known hearing, will note (see Fig. 26) -when the axis of the coil is in a plane (for instance the horizontal plane) nearly including the source amaXimumsOund when the source is in the (vertical)- transverse plane on, m, in. respect to the coil; silence when the source is inthe polar zones 5, s; and sound but lessening toward the polar zones 8-, s, as the coil is turned through the; angles m, s, in respect to the source." The silent'polar zones are sharply marked, and depend for angular magnitude on the structure of-the coil audits inductive core 'f The form illustrated in Fig. 12 and in Figs. 3' and' l presently to be referred to,

is characterized by polar zones of'silence decreasing in an 'ularmagnitude as the length of I the coi" is -increa se'd relative to its width. If sucha coil 40 with core a. referring now. to Fig. 20, is waterproofed and submerged, anda sheet metal tank Q carrying a running electric motor m resting on a sonnd-insulatingpad g is floated on the water, the coil- .0 is found to transmit the sound of the motor according to the relations of silence and maximum sound distributed about the vertical at the coil 10 as shown in Fig. 26 and above referred to.. The intensity of the sound received varies with the oriental-- tion of the source, but a marked emission is received at the detector at any azimuth of the exciting motor.

Referring now to Figs. 9. 15. 16 and 17, if two like fiat coils wound in layers w. Q08, are connected as shown'in Fig. 1."), the respective windings'being in the direction of the arrows, and the two coils placed in series across the terminals a. n as indicated. then the lmpact of either a sound wave or the em1s1on from a. motor or alternating cur- .renttransformer in the direction .r is without effect to produce an oscillation in the circuit Q07, 0.. 2, a, 452 I If now the coil m is replaced by'a coll 11: Flg. 16, wound in the same direction as the 0011 w, the. connections being as before, impact of a wave pm of a given number of turns, sensitiveness may then be d1m1n1shed as the core 3 3 1s in the direction 50 sets up 'an oscillation current in the circuit to", a, 2, a, 10". If either of the coils w, 10, is turned into the plane ofthe direction of the wave m, as shown in Fig. 17, no oscillation is produced. If such a coil as 10 is surrounded by. a wrapping of iron strips as at i, Fig. 9, sensitiveness is increased.

If a number of like coils d,'Fig. 17 all wound in the same direction and lying in the same plane are connected in series with a, a, and excited by a constant radiation in the plane of the figure, the intensity of their effect at T will be found to be greater than that of one of them isolated by a wire n 'or two of them isolated by a wire' n If new the direction of the oscillation due to two of them be reversed at switch n there is no response at T. If a laminated loop of iron wire 9 17, be wound with a coil 1.0 and excited by a constant radiation perpendicular to the plane of the loop, giving a soundofa certain intensity at T, the sound is not diminished when the coreis cut at W, nor when it is cut away further to y, y but for a coil shortened beyond a critical length.

Referring now to Fig. 8, if a magnet N S bent into the form of an interrupted annulus of considerable dimensions (and having a natural sound vibration period) be provided with soft iron a'rmatures n's wound with a few turns of wire 10 and these armatures are placed on the large magnets N S as illus trated in Fig. 8, so as to bridge the gap in the annulus, and the coils on the armatures are then connected as shown in parallel to the terminals a, a, the resulting instrument will be found to be sensitive to a wide range of 'sounds'approachingjt in: any direction,

theoutput in the clrcuit a, w, a, being an oscillation wave closely similar to the sound wave but stripped of irregular and noisy overtones. A scratchy phonograph recordafor instance, is transmitted by the device of Fig. 8 without the scratchy sounds. The emissions of motors, oscillating discharge circuits, and transformers are also received.

If now, instead of the detector devices mentioned, and referring to Figs. 2, 2 and 2 a laminated ring core of-soft iron, for instance, a strip'g cut from sheet' iron about 1 /64 of an inch thickand about 2 inches wide and turned up into a spiral ring 9' about 6 inches across is covered with a padding 9 of cotton batting or felt, and then wound with a vortex winding of about 450 turns of insulated copper wire, for instance about No. 18, an instrument (1 as shown in Fig. 1 having marked sensitiveness is formed. 1

If now the detector d is connected in series with terminals a, a, and placed to receive the impact of a. sound wave propagated in the direction of the arrow :20, Fig. 19, as shown at I, with the central axis of the ring in direction a", the sound is transmitted to the telephone T with extraordinary vigor and clearness. That is to say, this occurs if the sound does not inthe particular instance mentioned fall below a pitch of about 200 vibrations per second or exceed a pitch of about 10000 vibrations per second. Within these limits musical sounds and articulate speech arriving int-he directionaof the arrow 01?, that is to say, in the axis of the torus, are transmitted with great purity of reproduction, and thebetter transmitted the better the resonance and purity of the sounds received. Certain classes of noises such as pouring water into a vessel, scratching sounds, and

dull rubbing or rumbling sounds, are transgap h as indicated in the feet, with a spark of half a millimeter, is

audible at the telephone T when the instrument 0. is in the position I with respect thereto. Turning the instrument d to the positions II or III does not very greatly change the effect.

Referring to Fig. 19, the blast of asmall organ pipe p (512 vibrations per second) at about 400 yards and inaudible to the observer is transmitted ,clearly when within five or ten degrees of the direction x, the instrument (Z being in position I. When the instrument is turned to the position II or III the organ pipe at this distance is inaudible.

Time of transmission of the sound is the ex pected time of the sound-wave in air.-

-We do not fully know and therefore do. not undertake to explain with authority-the reasons for, the behavior of the apparatus ,ment-ioned. Upon the classic researches of l -Ii.

such waves when taking place in a coil su'rrounding a magnet not only have a demagnetizing effect but also suppress the hysteresis in iron bodies in a changing or fluxing state of magnetism. [Rutherford; Marconi; G.-Maurain; E. Madelung]. l I

From this, it follows-that such '-a wave; whether ornot plane-polarized in the direction of its magnetic effect may directly (a). shift the molecular structurc'or magnetic. constancy. of a mass of iron (7)) directly, at-

fect a conductor circuit having parts in and parts not in the plane of polarization. and therefore cause a difference of potential between the parts of said circuit or (0) in the case of a closed circuit having a magnetically inductive relation to a body of iron ex-. posed to such waves, cause a difference of I potential and flow in said circuit dueboth to cause (a) and to cause (b); I

For further hypothesis. wegconceive that a body having a rapidly changing magnetism, sueh as the fieldof a motor; or dynamo or core of a transformer ((l) emits Maxwells or -Hertzs waves by stress on the ether much as the charge in a condenser sets up a stress in the dielectric surrounding it, but (e) that these waves are plane-polarized in the direction of their magnetic manifestation, and hence are imperceiva'ble by the electric wave detectors of common knowledge; (7) that their energy is nevertheless availble at a distance to induce an electroinotive. force in conductors arranged according to the present disclosure.

From the experiments noted above, we further conclude that a hysteretic or intramolecular change ina metal under impact of such waves is an observed fact.

We further advance for hypothesis only that a change having a similar effect on the metal conductors and cores mentioned is induced by acoustic'vibrations of certain frequencies, if not of all frequencies, and that such electromagnetically produced and acoustically produced change in the cores or coils, or both, of the described apparatus is the causative factor in the observed potential differences changing at the frequency of the original impulse. as found in detector circuits of the general type herein mentioned when exposed to excitation by radiations having a magnetic or acoustic component.

For. ractical utilization, referring to Fig. 21, Sue an instrument as (1 may have its wire coil covered with paratlin or other waterproof insulating protective coating, and be used submerged to detectsubmarine radiations. A submarine bell B of the exist; ing type on our coasts, for an instance of such uses, has been observed'to excite such a detector d at distances of 2 miles, with no indication that the maximum distance was approaching. Neither passing steamships, the wash of the water, nor the internal noises of the vessel V from which the detector d was suspended overboard and on which instrument A was carried, were confusingly audible. The noises of the screws, of the ,as a faint background A reliable.

\ K water washing-on the instrument and the. .vcssel were mandible, and the sounds made by the reciprocating engines of the vessel V and passing \vate1--t1'aflic were audible only for the bell signals. \V hen the detector was submerged in an internal water-tank at the bow of'the yesscl V, the signal sounds were little diminished or c(")nfused-, but indication of their direction made by turning the detector was no longer It. will-be understood that the detector ll .isbut one instan e of-detectors having capacity to respond to acoustic or otherjradiant wave excitation and to indicate the direction of the wave. For instance, as shown in Fig. 6, the core 1 of an annulus such as (l' may be made of a coil of many turns of soft iron wire with advantage; or as detector (1 may be wound endwise through and on an elongated solid or laminated tubular core 1, Fig. (5; or radially on a disk core 9, Fig. 7; or a tubular soft iron core 0 Fig. 3, may be wound with several layers of relatively coarse insulated wire w as shown in Fig. 3, to form a detector (i Another form of detector (Z Fig. 4, may comprise a wood or fibre spool 9 a core formed of a bundle g of soft iron 'wires, and a winding 10 of rela Or as shown inFigs. 5"

tively coarse wire. and 5, an annular iron channel g with a peripheral coil Q05 may comprise another form of detector (Z narrow angular range of maximum sensitivencss toradiations propagated in or near the relative direction m and a wide zone of silence placed in or on either side of the direction of propagation of the wave, as shown in Fig. 26.

In respect to the three general types of detector which are merely illustratively shown at (Z and d for one type, at d" for another type, and at (Z for a third type, the first type ((l", d) is characterized by sharply marked polar zones of-silence, so that absence of indication of a radiation as the detector is turned with respect to the source of the radiation is indicative that the direction of propagation of the radiation lies within a few degrees of the direction of the axis, the direction being capable of being found within a degree or two of are by talc ing the mean between recurrences of the.

The detector at has a when the axis of the detector is typp (Z'.

ular to its axis is in the line of propagation of the radiation. Inthe types (1 and II" sensitiveness to emissions such as made by operating electric motors as compared with acoustic sounds is more marked than in shield S in a. horizontal position, Fig. 23,

andthe detector a? remains insensitive to v radiations propagated in any horizontal or vertical direction.

B ut if the detector cl is turned into the position shown in Figs. 24 and 25, the detector will be found to be insensitive to radiations proposed in the direction 00 m". but sensitive to those propagated in directions along or nearly-in the direction of the axis of the shield S (perpendicular to the plane of the figures).

Each form of detector described has been found selectively to transmit, in respect to sound waves, and periodically recurring magneticor electric waves pure tones and. their harmonics in preference to mixed and broken tones. B'y hypothesis and experiment, the pitch sensitiveness of each detector has as factors the number of spires or turns of wire upon it, the quality. weight, distribution and dimensions of the magnetically inductive mass comprised in it, the capacity of the. detector. and the capacity, inducdance and impedance of the transformer 2 of and leads to the amplifier A. In the tase of detectors of the type (Z3, 03*, the longer the core and the more theturns of wire, the

.lower in pitch are the waves or recurring wave-trains strongly exciting the detector circuit. In the case of the type d, the narrower and larger the annulus. the more marked is the sensitiveness to direction of propagation in the plane of the annulus.

Detectors of the typesd d, or (Z and other types to lesser degrees, areserviceable as indicators of the direction of propagation of plane polarized electric or Hertz waves impinging upon them. When thepolar axis of such a detector is perpendicular to the direction of a known source of such waves,

the telephone T is responsive. Turning the detector through a few degrees of are away from this .position (how far depending on the vigor of the signal) extinguishes the indication from sucli waves. Quantitatively, such detectors give but feeble responses to the usual signals as compared with many known forms of wireless receiving apparatus, but we are not aware of any prior of the detector (Z from the horizontal. -rent loads 70 from detector d to terminals apparatus indicating-the direction of the wave with such certainty.

\Ve may utilize the selective sensitiveness of detectors of the genus described in many different ways. As mentioned above, each typeappears to be sensitive in a superior degree to high-pitched emissions found to be made by running. starting and stopping electric motors. by alternating current transformers, and by dynamos. The invention therefore affords a method ofand means for detecting the approach and position of a vessel containing operating electric motors,

transforn'iers or dynamos by selectively per-- ceiving and determining the direction of propagation of the radiations emitted in or above the water by. such a vessel.

Referring to Figs. 27, 28, 29 and 30, an observing vessel V' may be provided with a mounting l) for detector (1 of one of the types-indicated above, and means for turning this detector in azimuth and in altitude to known departures from the fore and aft axis of the ship. one instance as shown in Fig. 27, of convenient means, may comprise a manhole 50. and stuffing-box gland 51 in the ships bottom in which gland is jour naled a .tubular shaft 53 having" an index sector 54 and handle 55 fast thereto above an upper bearing- 56, which may be on deck, and may carry a graduated azimuth circle :37. At its lower end the shaft 53 carriesa fork (30 in which horizontal trunnions 61 on-a saddle 62 are journalcd. Saddle 62 -carries a detector (1 whose polar axis is at right angles to the trunnions; Saddle (32 and detector d are preferably arranged to be turned on the axis 61 to known altitudes of the polar direction of the detector 0?. For instance, a bevel gear sector 63 attached to saddle 62 is adapted to be turned by a mesh-' ing bevel gear 64 on a tubular altitude shaft 65' within shaft. 53. and having an index 66 and handle 67 for reading in respect to the index sector 54 departure of the polar Caxis a, a, of amplifier A are carried within shaft 65 Referring to Fig. 30. suppose the altitude shaft 65 at D be turned so that the polar axis of the detector, such as (l is vertical. Then bearin' in .mind the near] maximum sensitiveness on a wide are central on.

the transverse axis of the detector, approach of a submarine U having a' running motor or dynamo abroad at any bearing to the ship V gives warning by a loud, highpitched hum audible at telephone T. The observer immediately turns the altitude handle 67 to position the detector with its axis horizontal. 4

If the azimuth handle 55' is positifjned on the fore and aft, axis, and the submarine U is abeam either to port-or starboard, the

i sound continues. But. ifith e submarine IS dead ahead or astern, the silent polarzone of'detector d covers it, and the sound ceases at T. \Vhenever the indication is abeam,

the observer sweeps the handle to find the bearing of the maximum plane, and then the center of the silent zone. The latter readinggives the bearing of the source of the sound within a few degrees of arc. The whole operation-has taken but a few seconds.

Whether the sound is ahead or astern (or to port or starboard) of the plane found is stil unknown. To determine this the ship may carry fixed or movable detectors D D4, on her sides. .These may be of any type,

- such as the type d.. By suitably arranged ship V is provided with bearing brackets 71, 71, for an overboard vertical shaft 72, which may be tubular to house the current leads 73, and terminate in a fork 74; in which a horizontal detector 01 is pivoted for a limited motion on trunnions 75 as controlled by a link 76 and bell-crank lever 77 having a pointer 78 reading on a sector 78 on a sprocket wheel 79 fast to the top of shaft 7 2. A chain 81 to inboard hand-wheel 82 on a standard 83 provides a convenient azimuth adjustment for shaft 72, which may be read at a compass 84. -A vertically placed detector d is fastened to shaft 72 at right angles to trunnions 75. A double-pole switch 85 serves to connect either cl or d to the amplifier A; at will.

Detector. al is-sensltive in all horizontal directions. Having given warning of asubmarine U, contact at 85 is switched -to detector d, and the wheel 82 turned to sweep the vertical sensitive plane of detector d past the directionofthe source, which is read at the compass 84 when found. De-

tector d may be moved'by lever 77, when thesubmarine'isnear' by' to give direction by inclination to the horizontal of its plane of maximum sensitiveness, and indication of its depth, the switch 85 being again shifted when the bearing in azimuth is known. r I

It will be apparent that two boats V, 'V,

. equipped with the devices mentioned may point to and either converge upon the submarme U, one of them attacking her when dead ahead of the other (and so over the source of the radiation) or by the intercept of their fore and aft lines giving an infallible indication of the position of the submarine for a third "essel equipped to capture or destroy. Or a merchantman equipped wlth the device may be given indication ofa safe direction of retreat and-constant warning of approaching danger. Vessels equipped wlth our device may exchange signals either by a submerged bell, a submerged magnet excited by an alternating current adapted to be made and broken, by causing spark discharges: or other sources of excitation at distance, or

hearing and distances of a submarine or other. source-of radiations by the azimuth of the respective detectors with respect to the line joining them. For this and other purposes, such a detector may be mounted on a float towed behind a vessel, not shown.

A single vessel equipped with the described devices may rely upon a detector mounted to be moved on a horizontal axis, or fixed with its sensitive plane in the vertical, to

indicate when the submarine is immediately below "her, having approached on the line of propagation of the emission from the motors. In either case, finding the enemy and his destruction is made. certain.

We have hereinafter referred to the phenomena of the creation of a relatively feeble oscillating flow in the detector circuits described by an acoustic disturbance, as a direct. conversion of the acoustic wave energy into electrical disturbance. This is to be distinguished from first mechanically transforming the sound wave .energy into motion of a diaphragm, a magnetic body, or a member of an inductive couple, and then converting mechanical energy of'this moving mass into an electrical distur nce.

The direct conversion referred to avoids the transformation of the radiant energy int mechanical motion.

We claim: 1. The art of perceiving radiant energy of acoustic,- type comprising transforming the energy of an undulation of such type into a corresponding and perceptible electric current in a conductor coil having there-' in a uniform potential except when excited by exterior acoustic energy arriving in a certain direction in relation to said coil and causing the said current toproduce an am plified current in an observation instrument.

2. The art of perceiving the direction of propagation of sounds comprising contemporaneously transforming the energy of the acoustic wave into electrical energy in a detector circuit capable of being excited to different degrees of electric energy according to the directioniof propagation of the sound at the detector, and containing no other source of energy, and observing the v during different orientations of the detector.

3. The art of perceiving Wave-disturbances in media capable of acoustic vibration comprising direct conversion of a part of theenergy of the acoustic wave-disturbance into a relatively feeble electrical disturbance in a conductor immersed in said medium and causing amplification of the said electrical disturbance.

4. The art 7 of perceiving wavedisturbances in and of media capable of acoustic vibration comprising direct conversion of the energy of the wave disturbance of the medium of transmission into electrical di s turbance of like frequency in a conductor immersed in said medium.

5. The 'art of perceiving wave-disturbances in and of media capable of acoustic vibration comprising direct conversion of the energy ofthe wave-disturbance of the medium of transmission into electrical disturbance of like frequency in a conductor immersed in said medium and employing the electrical disturbance so created to excite the flow at like frequencies of local currents of much greater magnitude adapted to be audible in a telephone receiver.

6. The combination of a direction-sensitive sound-wave detector, and amplifier for receiving indication therefrom, and a mounting for thedetector permitting it to be turned in altitude and azimuth.

Signed by us at Boston, Massachusetts, I

this eleventh day of April, 1918; 

